The present invention relates to an apparatus for and a method of achieving a low frequency vibration type washing by utilizing a resonance phenomenon of a multi-phase medium made of water, detergent and air caused by a particular frequency.
Generally, existing washing machines employ a pulsator washing system including a pulsator installed on the bottom of a washing tub and adapted to wash clothes by rotating in normal and reverse directions. However, such washing machines have a problem of clothes getting tangled because the pulsator rotates alternatingly in normal and reverse directions. For solving such a problem encountered in the pulsator washing system, various positive research efforts have been made recently. One of the washing machines that resulted from these research efforts is a low frequency vibration type washing machine.
FIG. 1 is a schematic view illustrating a conventional low frequency vibration type washing machine. As shown in FIG. 1, the washing machine includes a washing tub 1 containing water, detergent and clothes to be washed therein, a low frequency oscillating vibrator 2 disposed on the bottom of washing tub 1 and adapted to generate a resonance phenomenon at a multi-phase medium made of a washing liquid (water and detergent) and an air layer, and a linear motor 3 adapted to drive the low frequency oscillating vibrator 2. A drive shaft 4 extends vertically through the bottom of washing tub 1. The drive shaft 4 connects the low frequency oscillating vibrator 2 to the linear motor 3 so as to transmit a reciprocating movement of the linear motor 3 to the low frequency oscillating vibrator 2. The washing machine further includes a low frequency generator 5, adapted to generate a waveform having a frequency band ranged from 20 Hz to 250 Hz, an amplitude ranging from 2 mm to 25 mm and a rotation angle amplitude ranging from 2.degree. to 10.degree., and thereby drive the linear motor 3, an amplifier 6 adapted to amplify an output signal of the low frequency generator 5 and apply the amplified signal to the linear motor 3, and a pressure sensor 15 adapted to detect the pressure of water supplied in the washing tub 1 and measure the level of the supplied water in the washing tub 1.
Operation of the conventional low frequency vibration type washing machine having the above-mentioned construction will now be described.
First, as the low frequency generator 5 generates a waveform having a frequency band of 20 to 250 Hz, an amplitude of 2 to 25 mm and a rotation angle amplitude of 2.degree. to 10.degree., the amplifier 6 amplifies the generated waveform and then sends it to the linear motor 3.
Upon receiving the waveform generated from the low frequency generator 5, the linear motor 3 is actuated, so that the low frequency oscillating vibrator 2 connected to the drive shaft 4 of the linear motor 3 can oscillate. As the low frequency oscillating vibrator 2 oscillates, a resonance phenomenon occurs at the multi-phase medium made of the water, detergent and air layer contained in the washing tub 1. The resonance phenomenon generates small air bubbles in the multi-phase medium while generating cavitation phenomena or non-linear vibrations thereof. As a result, the mechanical energy obtained by these cavitation phenomena or non-linear vibrations of small air bubbles is combined with the chemical action of the detergent in the multi-phase medium, thereby enabling a washing or cleaning to be effectively carried out.
The linear motor 3 serves to linearly reciprocate the drive shaft 4 in the vertical direction so that the low frequency oscillating vibrator 2 can vibrate at the same frequency as the resonance frequency of the multi-phase medium. The range of the linear reciprocating movement of the drive shaft 4 is determined by the amplitude of the drive waveform applied to the linear motor 3.
As water is supplied in the washing tub 1, the water level in the washing tub 1 is increased. For controlling the water level in the washing tub 1, the pressure sensor 7 detects the pressure of water contained in the washing tub 1 and converts the detected water pressure into an electrical signal which is, in turn, transmitted to a control unit not shown.
However, the conventional low frequency vibration type washing machine has the following problems.
Although the low frequency generator 5 generates and outputs a constant low frequency, the vibration amplitude of the low frequency oscillating vibrator 2 may be non-uniform due to factors involved in the system itself or external factors. For this reason, the washing and cleaning efficiency may be lowered.
Furthermore, the conventional washing machine is not equipped with any system for detecting the vibration amplitude and controlling the output frequency of the low frequency generator 5. As a result, it is impossible to control an accurate vibration amplitude based on water level and predetermined control value.